Facial numbness is a distressing symptom most commonly limited to one side of the face, although both sides are sometimes affected 5. The numbness can manifest as reduced sensitivity to a complete lack of sensation. Facial numbness occurs with a wide range of medical conditions, some much more serious than others 5. The specific part of the face affected and the presence or absence of accompanying signs and symptoms help narrow the lengthy list of possible culprits.

Traumatic Nerve Damage

The trigeminal nerve -- also known as cranial nerve V or CN V -- carries sensation signals from the face and front of the scalp to the brain, where they are interpretted. Traumatic damage to any of the three branches of this nerve can lead facial numbness 5. This might occur due to a facial or skull injury, or accidental nerve injury during a dental procedure or surgery involving the face or brain. The three branches of CN V on each side of the face and the areas they innervate are:

Nontraumatic Nerve Damage

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A variety of ailments can lead to nontraumatic trigeminal nerve damage and facial numbness 5. Longstanding diabetes can damage nerves anywhere in the body including branches of CN V, although this is uncommon. Sickle cell disease can cause damage when mishapen red blood cells block capillaries and deprive the nerve(s) of oxygen. A molar tooth abscess can potentially damage a branch of CN V by compressing it. Head and neck, facial skin cancers, and cancers that spread from elsewhere in the body can cause facial numbness if they compress or invade a branch of CN V 5.

Facial numbness can accompany certain cranial nerve disorders 5. Bell palsy, for example, primarily affects the facial nerve causing temporary paralysis on one side of the face. For reasons that are incompletely understood, the trigeminal nerve can also be involved leading to facial numbness on the affected side 5. Another condition called trigeminal neuralgia is characterized by brief but excruciating shooting pains in the face. Between these episodes, the affected side of the face typically exhibits decreased sensation.

Central Nervous System Disorders

Several disorders of the central nervous system -- the brain and spinal cord -- can potentially cause facial numbness 5. Tumors involving the brainstem might cause this symptom, which is usually accompanied by other signs and symptoms that vary depending on the exact location and size of the growth. Acoustic neuroma, a noncancerous tumor of the nerve that carries signals betweeen the inner ear and brain, can cause facial numbness and weakness along with hearing loss, ringing in the affected ear and a spinning sensation 15.

Stroke and a transient ischemic attack -- commonly known as a TIA or mini stroke -- are important considerations with sudden facial numbness 5. Multiple sclerosis can also cause facial numbness, although this is uncommon 5.

Other Causes

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• Bleeding into the brainstem
  
• Brainstem blood vessel malformation
• Cholesteatoma, a noncancerous middle ear tumor
• Pituitary gland tumor
• Certain drugs, such as:

• fertilizers
  
• pesticides
  
• arsenic
• Brass instrument (trumpet
  
• tuba or French horn) neuropathy
  
• a cause upper lip numbness
• Rarely
  
• systemic lupus erythematosus or rheumatoid arthritis

Warnings and Precautions

• Sudden, severe neck pain or headache
  
• Sudden visual changes, such as vision loss or double vision 
• Sudden dizziness or a spinning sensation
• Numbness, weakness or paralysis on one side of the body
• Slurred speech, difficulty swallowing or drooling
• Confusion, agitation, drowsiness or other mental changes
• Decreased coordination or difficulty walking
• Unequal pupil size
• Involuntary eyeball movements
• Drooping jaw or upper eyelid :